1. Field of the Invention
The embodiments disclosed herein relate to a matrix converter.
2. Description of the Related Art
A matrix converter has a plurality of bidirectional switches connecting an alternating-current (AC) power supply and a load. With these bidirectional switches, each phase voltage of the AC power supply is directly switched, thereby outputting an arbitrary voltage/frequency to the load.
It is known that, theoretically, a matrix converter is capable of outputting an undistorted sinusoidal voltage up to 0.866 times the fundamental wave of an input voltage. Depending on applications, a matrix converter is desired to be operated in an area where the output voltage saturates (hereinafter referred to as a “saturation area”).
In the case of driving an induction motor, for example, there is technology that controls the output voltage to be a sinusoidal wave by controlling a magnetic flux to be weakened in a saturation area (for example, see Japanese Unexamined Patent Application Publication No. 5-260762). With this technology, the output voltage increases by an amount equal to the weakened amount of the magnetic flux.
In this regard, technology that moderates an increase in an input current in a saturation area by multiplying an output voltage command by a gain in the saturation area (for example, see Japanese Unexamined Patent Application Publication No. 2008-259380) is proposed.
However, the technology which multiples an output voltage command by a gain in the saturation area has a problem that the input current becomes distorted because the output voltage is distorted.